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Joe Posnanski writes about sports for a living, particularly baseball. Here, he writes about sports and also Springsteen, Hamilton, Harry Potter, iPads, infomercials, his idolization of Duane Kuiper, his family and magic. He lives in Charlotte with his wife Margo, two daughters Elizabeth and Katie, and their dog Westley. Joe is currently working on a book about Harry Houdini in today’s world.

If so, the thing isn’t even accurate. A Cubs-Padres game in 2017 most definitely does not begin at 50/50 win probability. And as the game goes along the talent level of the players likely to play each inning still to come has an effect on win probability too.

W.P. is a junk stat because of all the relevant facts it doesn’t even consider.

“A Cubs-Padres game in 2017 most definitely does not begin at 50/50 win probability.” — It does, and it should. If the Cubs players perform well, and the Padres players don’t, the win probability for the Cubs will increase. This is exactly how WPA should work.

This doesn’t pass the smell test. Peak Pedro vs trough Jaime Navarro shouldn’t start 50-50. I mean, I get the construct, but even if you don’t consider things like pitcher or team quality, shouldn’t the home team get a slight preference in keeping with their historic edge?

No. The home team’s advantage will be reflected in what they do in the game. You guys are criticizing WPA for something it doesn’t try to do: predict the chance of a team winning -before the game even starts-. The important thing that WPA does is to measure the -change- in win probability that happens during the game. You’re of course free to make your own version of WPA, that assigns whatever to the initial win probability. But that won’t have any extra value.

This makes sense, thanks. I guess the quibble is with the name. Saying Prime Pedro’s team and Trough Jaime Navarro’s team start a game with 50% win probabilities is false. In the context of the WPA stat it is constructed to be true, but in actuality it is false. (If you were forced to bet on Navarro’s team, you would not want even odds.) You will likely argue that fault lies with the (mis)interpreter; I will lay some of the blame on the name chosen for the stat, which assumes that one should know that the “win probability” assigned to a team is not meant as a measure of, well, the probability of a specific team winning.

Or consider this example at the extreme end. Suppose team A had 100% chance of beating team B. At the end of the game, which team A would win, both team A and team B would have a net WPA of zero, implying that team A played equally as well/poorly as team B. Now -that- doesn’t pass the “smell test”.

Joe, you only told half the story about the Angels drafting Mike Trout. Eddie Bane was the Angels scouting director who selected Mike Trout in 2009 (a draft in which he also selected Kole Calhoun and Garrett Richards). For that he was fired by Tony Reagins in 2010. Reagins and Bane did not get along, and Bane’s phenomenal draft was seen by Reagins as a threat to his authority, and so Bane was sent packing, along with Greg Morhardt, the area scout who had recommended Trout. A year later, Reagins traded Mike Napoli and Juan Rivera to the Blue Jays for Vernon Wells and his albatross of a contract, one of the worst trades in baseball history, and Reagins too was let go. The Angels farm system has never recovered.

So it is ironic that of all the scouting directors who agonized over passing on Mike Trout, the only one who paid a price for it was the guy that made the pick.